Rocket Mass Heaters

A rocket mass heater is a space heating system developed from the rocket stove, a hybrid with elements of an efficient wood-burning stove and a masonry heater. Wood is gravity fed into a “J-shaped” combustion chamber, from where the hot gases enter a heavily insulated metal vertical secondary combustion chamber, the exhaust then passes along horizontal metal ducting embedded within a massive thermal storage.

The thermal storage is large enough to retain heat for many hours and typically forms part of the structure of a building. Rocket mass heaters have proven to be popular with natural builders and within a permaculture designs. They are normally self-built and are not yet recognized by all building codes which regulate the design and construction of heating systems within buildings.

The rocket mass heater works on similar properties as a masonry heater. A fast, high heat and oxygen-fed fire burn up the volatile gases and particulates, leaving very little pollution, and turn almost all the fuel into energy. A bit of smoke is released during the first minutes of a fire, until the temperature in the chamber is hot enough to burn all gases.

The major difference between a masonry heater and a rocket, is that the rocket stove has an insulated J- or L- shaped combustion chamber that forces the fire to burn horizontally. The fire then hits a 90 degree angle at the end of the chamber which causes a strong turbulence to rise up the insulated heat riser, creating a strong draft that feeds the intensity of the fire.

As opposed to the masonry heater which requires some advanced masonry skills, the rocket mass heater can be built by any enthusiast with basic masonry and engineering abilities. A rocket mass heater can usually be put together using recycled and natural materials, such as cob and bricks.